The present invention relates generally to a technique for retouching, or removing defects or blemishes from, an image, and more specifically to a method and apparatus for recalculating values of pixels selected or identified using a computer generated brush.
When using an image processing system, it is often desirable to alter one or more pixels in an image. For example, it is desirable to correct images containing defective or missing pixels caused by imperfections in the optical equipment used to acquire the image, such as scratches, smudges or other blemishes on camera lenses, photocopier platens or on the surface of the contact glass of a scanner. It is also desirable to manipulate images by replacing selected portions and filling in those portions with a continuation of the surrounding image. For instance, one may wish to alter a picture by removing a portion of the image, such as a person or writing on a wall, while maintaining continuity with the surrounding image.
Some techniques for replacing, or correcting pixels in an image typically employ low pass filtering. However, low pass filtering often tends to blur the image. Other techniques use extrapolation based on the nearest neighbors. That is, the value of bad or missing pixels will be extrapolated based on the value of neighboring pixels having correct or valid values. These techniques can also result in a blurred image, mostly because they do not allow for smoothing of the image when there is a large variation in color in the neighboring pixels. Extrapolation techniques also can result in visual discontinuities or other visual artifacts at the edge of the filled-in region. Thus, it is clear that what is needed in the art is an improved technique for retouching, or removing defects or blemishes from, an image.